Device for determining spectacle lens centering data

ABSTRACT

The invention relates to a device for determining spectacle lens centering data, comprising a housing ( 18 ) that is height-adjustable by means of a lifting column ( 10 ), said housing having a digital video camera, whose lens ( 20 ) are mounted together with a mirror ( 22 ) and a light source ( 24 ) in the area of the front surface ( 26 ) of the housing ( 18 ). Said device also has a digital computer ( 32 ) that is connected to the digital video camera, wherein the customer ( 40 ) can take position in a marked place ( 42 ), preferably at a distance of approximately 3 m, and an attachable clip ( 50 ) equipped with a sighting device ( 66 ) can be attached to the frame of the spectacles ( 41 ), whereby the required centering data can be quickly and precisely determined by means of a substantially automated computer program.

[0001] The present invention relates to a device for determining thecentering data for eyeglass lenses, i.e., to adjust optical lenses tothe parameters of a specific eyeglass frame.

[0002] Among the various parameters which must be adjusted to fit theeyeglass lenses correctly in the eyeglass frame and to make the opticalcenters of the lenses coincide with the visual axes of the eyes, it isusual to know the pupillary distance and the level of the pupils withrespect to the eyeglass frame.

[0003] It is also important to measure the level of the optical centersof the lenses with respect to the lower and upper edges of the eyeglassframe into which they are to be fitted.

[0004] The usual routine procedure employed by the optician—and thus thecurrently accepted prior art—is one in which the optician and client sitopposite one another and the client puts on a frame of his choicecontaining a glass disk. He is then requested to “look at a distantpoint,” after which the optician draws a hatch mark, based on his visualjudgment, on the disk or a ruled contrast film at the viewing referencepoint which he has sighted from his visual reference opposite theclient. The centering hatch mark determines the position of the opticalcenter of the eyeglass lens to be set in the frame.

[0005] This procedure is followed individually for each eye (monocularapproach)—with the result that one obtains, essentially empirically, thepupillary distance PD—including, however, all possible attendantimprecision from parallax, marking errors, etc.

[0006] The goal of the present invention is to create a device whichallows for a rapid and practicably precise determination of thenecessary eyeglass lens centering data.

[0007] According to the invention, this goal is achieved by a device fordetermining the eyeglass lens centering data, said device including ahousing which is height-adjustable by means of a lift column, thehousing supporting a digital video camera in which the objective lenstogether with a mirror and a light source is located in the region ofthe front panel of the housing; and including a digital computerconnected to the digital video camera, wherein the client may take up amarked position, preferably one approximately 3 m distant, with hisalready-selected eyeglass frame in front of the mirror, and wherein asuperposable frame is mountable on the eyeglass frame, the superposableframe being equipped with a sighting device with a scale from which thetilt of the eyeglasses is readable, the head position of the client andtilt of the eyeglasses being monitorable at the computer on the monitorscreen, and wherein the superposable frame has two calibration points ata predetermined spacing which matches the average distance between theeyes, the exact position of said calibration points being quickly andprecisely determinable by an essentially automated computer program onthe monitor screen after freezing the client image by controlling theindividual calibration points by a square box appearing automatically onthe screen and subsequently automatically determining the brightnesscenter point of the calibration points, the exact position of the tworeflection points of the light source on the cornea imaged on the screenalso being quickly and precisely determinable analogously in asubsequent program step by controlling said square box.

[0008] The device according to the invention is distinguishedspecifically by the fact that the determination of data by using thereflection points of the light source at the apex of the cornea of theright and left eye is effected very precisely. These reflection pointsare obtained as an essentially point-type reflected image of the lightsource at the apex of the cornea. The light source of the deviceaccording to the invention consists preferably of a ring illuminatorwhich surrounds the edge of the mirror which is designed as a circularmirror. The above light source may also consist of two illuminatorswhich are located on each side of the mirror edge, approximately at thelevel of the objective lens of the video camera, or preferablyapproximately at a level immediately above the upper edge of thisobjective lens.

[0009] The sighting device of the superposable frame advantageously hasan on-off-switchable locating illuminator, specifically in the form of alight-emitting diode, as well as a diffusing screen with a scale infront of which a preferably spherical bead of the sighting device islocated at a predetermined distance of approximately 20 mm, wherein anessentially point-type shadow on the scale of the sighting device iscreated when the spherical bead is illuminated, the shadow beingemployed to read the tilt angle of the eyeglasses, and wherein ahorizontal line of the scale, which line preferably matches theapproximately 11° tilt angle of the eyeglasses and is emphasized inthickness as the reference line, and wherein the additional horizontalscale lines above and below this reference line each represent a changein the eyeglass tilt angle of approximately 5°. The locating illuminatoron the superposable frame ensures that the client directs his gaze tothe reflected image of the illuminating locating illuminator in themirror at a preferred measurement distance of 3 m between the client andmirror, and thus at a real distance of 6 m, thereby meeting therequirement of viewing with a relaxed focus; in addition, thismeasurement may be performed in the examination room or in ancillaryrooms without interfering with general client traffic.

[0010] The rapidity of the measurement procedure is achieved by the factthat the computer is programmed so that the individual measurement stepsproceed essentially automatically and upon completion of a given stepthe tools and aids required for the next step automatically appear onthe monitor screen. The operator is thus guided through the measurementprogram, thereby accelerating the measurement procedure.

[0011] The main emphasis has been laid specifically upon the fast andpracticably precise determination of the required centering data. Anextremely important factor is the fact that operation is simple and maybe performed by any employee after a brief training period. Theserequirements were able to be met by the device according to theinvention which is not based on the previous method of measurement. Theinvention is based on utilizing the cornea reflection of a light sourcelocated at a distance of 3 meters. This reflection provides us with aprecise reference point for determining the centering data, whereas thedetermination of the measurement data based on the edge of the irisprovides only estimated values. In the device according to theinvention, preferably a plurality of preferably approximately 10×10 to20×20 pixels on the computer screen are selected when determining thebrightness center point of the calibration points for the superposableframe and/or of the reflection points of the light source on the corneaof the eye using the square box, only those pixels of the square boxbeing selected to determine the brightness center point for which thebrightness lies above an externally selectable threshold, and theevaluation proceeding by way of a weighted averaging in which a firstsum is obtained from the brightness of the selected pixels multiplied bythe X-coordinate, a second sum from the brightness of the selectedpixels multiplied by the Y-coordinate, and a third sum from thebrightness of selected pixels, the X-coordinate of the brightness centerpoint resulting from division of the first sum by the third sum, and theY-coordinate of the brightness center point resulting from division ofthe second sum by the third sum.

[0012] The following discussion utilizes an embodiment to explain theinvention in greater detail based on schematic drawings.

[0013]FIG. 1 is a side view of an embodiment of a measurement stand of adevice according to the invention.

[0014]FIG. 2 is a front view of the lift column shown in a side view inFIG. 1.

[0015]FIG. 3 is a perspective view of a superposable frame according tothe invention.

[0016]FIG. 4 is a perspective rear view of the superposable frame inFIG. 3.

[0017]FIG. 5 is a vertical partial section along line V-V of FIG. 3 onan enlarged scale.

[0018]FIG. 6 is a computer image of a client with the superposable frameover the selected eyeglass frame after aligning the head.

[0019]FIG. 7 is a view analogous to that of FIG. 6, after placing themeasurement hatch marks, and positioning the horizontal measurement lineat the lower edge of the frame and the two vertical measurement lines atthe left and right inner edges of the frame.

[0020]FIG. 8 is a view analogous to that of FIG. 7, but with additionalsubsidiary lines and the measurement result.

[0021]FIGS. 9 and 10 are a highly schematic view of the control panelsor windows appearing on the monitor.

[0022] To assemble the device according to the invention, the pedestal14 is set up and screwed on to the fixed section 12 of the lift column;then the front panel 26 together with the mirror 22 is unscrewed fromthe housing 18 and the housing 18 together with the camera mount and thelight source 24 are screwed on to the movable section 16 of the liftcolumn. The power cable (not shown) is then connected to pedestal 14,the computer cable (not shown) is plugged in to the provided socket, andthe plug of the lift motor also plugged in. Finally, the digital videocamera together with the objective lens 20 is carefully inserted in thecamera mount and secured, and the video camera is connected to thecamera cable. After securely screwing on front panel 26 which supportsmirror 22, the system must be adjusted, i.e., the lift column 10 withmirror 22 must be adjusted in height until the center of the mirror hasreached the zero-sighting axis 27 such that the head of the client isnow at the center of the mirror as well as at the center of the monitorscreen. If this is not the case, the image must be appropriatelyadjusted laterally and also vertically as required. The optical axis 28of the objective lens 20 of the video camera, which may have a focallength of 60 mm or 70 mm, must intersect the zero-sighting axis 27 ofthe client in the region of the eyes of the client; the image sharpnessand brightness may be adjusted at the camera.

[0023] After all the cables (not shown) of the device have beenconnected to the computer 32 and the main switch has been switched on,the image of the client 40 to be measured appears on monitor screen 34,the client preferably standing approximately 3 m away from mirror 22 oflift column 10 at a position 42 marked by metal feet (FIGS. 1 and 2).The superposable frame 50 is mounted on the already fitted eyeglasses 41of the client 40, the superposable frame being equipped with a sightingdevice 66 fitted with a light emitting diode 76 serving as a locatingilluminator (FIGS. 3 through 5). A switch 80 together with an actuationlever 83 and two button cells 44 are included in sighting device 66 ofthe superposable frame, the cells being integrated within an insulatingcomponent 72 which in turn is located in a generally hollow cylindricalcomponent 68. A scale 93 is located on the front side of thelight-emitting diode, from which scale the tilt of the eyeglasses may beread using horizontal lines 94, 95, 96, and 97. As the client tilts hishead, spherical bead 92 of sighting device 66 drops and the tilt angleincreases.

[0024] Computer station 30, specifically monitor screen 34, allows thecorrect head position of the client to be checked. Once the client is inposition, centered approximately three meters in front of mirror 22, themirror is raised or lowered by lift column 10 until the face of theclient appears at the center of the monitor screen. The client shouldview locating illuminator 76 through mirror 22 in a relaxed manner. Thelocating line on the superposable frame is centered by the client'sturning his head. This action ensures that the face is parallel to themirror. The image is now “frozen” by clicking the “Freeze Image” button(FIG. 9), and the measurement can performed.

[0025] The image may now be processed at leisure while the client leaveshis position and observes subsequent procedures. If the mouse cursor isnow moved to the right into the frozen image, the cursor automaticallychanges to a square box. This square box is used to select, for example,15×15 pixels of the screen which allow determination of the brightnesscenter point of a calibration point 62 or 64 of superposable frame 50,or of the brightness center point of the light reflections 42 or 44imaged on the screen from the cornea of the eyes. Within this squarebox, only those pixels are chosen for evaluation for which thebrightness lies above an externally-selectable predetermined threshold.The evaluation is performed by “weighted” averaging. The following sumsare generated from the three characteristics of the evaluated pixels:

[0026] 1. brightness multiplied by X-coordinate

[0027] 2. brightness multiplied by Y-coordinate

[0028] 3. brightness.

[0029] Dividing sum 1 by sum 3 results in the X-coordinate of thebrightness center point, and dividing sum 2 by sum 3 results in theY-coordinate of the brightness center point.

[0030] The square box is positioned by the left calibration point (62)of the superposable frame 50, although the white point 62 does notnecessarily need to be in the center of the box but only needs to belocated within the box, the location being unimportant.

[0031] Pressing the left mouse button causes the program toautomatically seek the center of the white point 62 and add a redmeasurement hatch mark 63. The operator then moves to the nextcalibration point 64 and repeats the process, causing the program toautomatically add measurement hatch mark 65. The operator now moves tothe white reflection point 42 in the left eye and then to reflectionpoint 44 in the right eye to add measurement hatch marks 43 and 45. Whenthe red measurement hatch mark 44 has been positioned in the right eye,a horizontal measurement line 46 automatically appears, and the mousecursor changes into a hand. The operator then causes measurement line 46to rest on the lower frame edges of eyeglasses 41 by moving the mouseup, down, left or right. He then clicks the left mouse button, and avertical measurement line 47 appears which is positioned at the leftinner frame edge. The operator then clicks the left mouse button andpositions the second vertical measurement line 48 which appears at theright inner frame edge. Clicking the left mouse button completes themeasurement procedure, and the measurement results appear at the bottomof the monitor screen, as shown with reference 104 in FIG. 8. The twocenter distances RD are indicated here for the right and left eye, aswell as the vertical distances from the lower lens edge to measurementpoints 43 or 45, thus providing the required data to produce a preciselycentered pair of eyeglasses.

[0032] In the screen shot shown in FIG. 9, there is a bar 100 located atthe left of the screen with buttons 111 through 124 and associatedexplanations 102, which only appear, however, if a button is activatedwith the mouse cursor by positioning the mouse cursor over the buttonand clicking with the left mouse button.

[0033] Images saved earlier may be accessed by “Load Image” button 111.Clicking this button produces the window shown in FIG. 10. The names ofall previously saved images are listed. To facilitate orientation,clicking a name produces a preview of the image on the right side of thewindow.

[0034] Double-clicking or selecting “Open” produces the image on themain screen as well as all measurement data.

[0035] Clicking “Save Image” button 112 saves all images recorded by thecamera.

[0036] Images may be saved with or without measurement data, regardlessof whether they are saved before or after eye measurement.

[0037] Saving can also be performed after measurement by clicking “OK.”

[0038] Selecting “Camera On or Freeze Image” button 113 turns the cameraon. The client's face is now displayed on the screen. Depending on theposition, mirror 22 must be moved up or down until the face is situatedat the center of the screen. Pressing the button again freezes the imageand measurement can proceed.

[0039] Button 114, “Brightness, Contrast and Color Saturation,” allowsthe brightness, contrast and color to be adjusted.

[0040] This feature allows the image quality to be enhanced in case ofunfavorable lighting conditions. Normally, this is not required however.

[0041] Clicking “Lower Mirror” button 115 allows the mirror to be moveddown.

[0042] Clicking “Lower Mirror” button 116 new allows the mirror to bemoved down.

[0043] Button 117 is intended for manually positioning the crosshair. Ifthere are problems with automatic centering, the measurement hatch markmay be positioned manually after selecting button 117. For the nextmeasurement point, the system again reverts to automatic centering.

[0044] When “Back” button 118 is clicked, the computer returns to thebeginning of the measurement procedure. All data obtained since themeasurement was begun are lost.

[0045] Clicking “Print” button 119 prints the image and measurement dataif the system is connected to a printer.

[0046] Button 120, “Enter Distance Between Calibration Points,” is onlyused when a new superposable frame 50 is employed and when the device isfirst started up. It allows the distance between calibration points tobe entered.

[0047] Clicking button 121, “Brightness Threshold for AutomaticCentering,” changes the response threshold if problems occur withautomatic centering due to unfavorable lighting conditions. Thisfunction is normally not required.

[0048] Clicking “Select Lens Table” button 122 allows the lens table ofa given manufacturer to be selected. Double-clicking the name of themanufacturer or entering the name causes the lens table to be accepted.“Select Lens Table” allows the lens table to be accepted.

[0049] Selecting button 123 displays the terms of the copyright.

[0050] Selecting “Exit Program” button 124 closes the program.

[0051] Before turning the system off, the computer must be properly shutdown.

[0052] A fundamental advantage of the device according to the inventionis the fact that the use of mirror 22 doubles the distance, therebyallowing a distance of 6 meters to be obtained even in confined spacesso that a nearly parallel orientation of the axes of the eyes isachieved.

[0053] Since the viewing axis of the client is aimed precisely in thecenter of mirror 22 surrounded by ring illuminator 24, the image of thering illuminator obtained is in the form of a bright spot on the corneaof the eyes. Based on these reflection points, pinpoint measurementaccuracy with virtually unsurpassed precision, of the reflection pointsand of the distance between them may, be obtained on the computerscreen.

[0054] Superposable frame 50 includes a support 52 on which retainingmeans 54 provided with spring-loaded arms 55, 56 are located betweenstops 58 which are slidable and securable using screws 59, the supportbeing connected by link 53 and screw 57 with projection 70 of sightingdevice 66, the light-emitting diode of which is located in a cavity 75of the translucent cylinder 74 and connected via its connecting wires 77and 78 to one pole of the battery 84 or the pin 81 of the switch 80, thesecond pin 82 being applied to the other pole of the battery, whereinthe one spring lock washer 86 producing an axial spring load, which issupported on one side by clamping ring 85, presses components 72, 80,84, and 74 axially together and in front of collar 69 of hollow cylinder68.

[0055]FIG. 8 Result RD right 32.3 RD left 30.6 Lens MultigressivPerfolit Height right 32.5 Height left 34.8 Type G Diameter 60

[0056]FIG. 9

[0057] Load Image

[0058] Save Image

[0059] Camera On or Freeze Image

[0060] Brightness, Contrast, Color Saturation

[0061] Mirror Up (optional)

[0062] Mirror Down (optional)

[0063] Place Crosshair Manually

[0064] <<Back

[0065] Print

[0066] Enter Distance between Calibration Points

[0067] Brightness Threshold for Automatic Centering

[0068] Select Lens Table

[0069] Info

[0070] Exit Program

[0071]FIG. 10 Load image Search in Image [Files]: Images Eyeglasses.bmp(Empty) Eyeglasses90.bmp Test1.bmp . . . . . . File Name Open File TypeCancel

1. Device for determining eyeglass lens centering data, said device:including a housing (18) which is height-adjustable by means of a liftcolumn (10), the housing supporting a digital video camera in which theobjective lens (20) together with a mirror (22) and a light source (24)is located in the region of the front panel (26) of the housing; andincluding a digital computer (32) connected to the digital video camera,wherein the client (40) may take up a marked position (42), preferablyone approximately 3 m distant, in front of the mirror (22) with hisalready-selected eyeglass frame (41), and wherein a superposable frame(50) is mountable on the eyeglass frame, the superposable frame beingequipped with a sighting device (66) with a scale (93) from which thetilt of the eyeglasses (41) is readable, the head position of the client(40) and tilt of the eyeglasses (41) being monitorable at the computer(30) on the monitor screen (34), and wherein the superposable frame (50)has two calibration points (62, 64) at a predetermined spacing whichmatches the average distance between the eyes, the exact position ofsaid calibration points being quickly and precisely determinable by anessentially automated computer program on the monitor screen (34) afterfreezing the client image by controlling the individual calibrationpoints by a square box appearing automatically on the screen andsubsequently automatically determining the brightness center point ofthe calibration points, the exact position of the two reflection pointsof the light source on the cornea imaged on the screen also beingquickly and precisely determinable analogously in a subsequent programstep by means of said square box, the exact position of the tworeflection points (42, 44) of the light source (24) on the cornea imagedon the monitor screen (34) also being quickly and precisely determinableanalogously in a subsequent program step by controlling said square box.2. Device according to claim 1, characterized in that the light sourceconsists of a ring illuminator (24) which surrounds the edge of themirror (22) which is designed as a circular mirror, or consists of twoilluminators which are located on each side of the mirror edge,approximately at the level of the objective lens (20) of the videocamera, or preferably approximately at a level immediately above theupper edge of the objective lens (20) of the video camera.
 3. Deviceaccording to claims 1 or 2, characterized in that the sighting device(66) of the superposable frame (50) advantageously has anon-off-switchable locating illuminator, specifically in the form of alight-emitting diode (76), as well as a diffusing screen with a scale(93) in front of which a preferably spherical bead (92) of the sightingdevice (60) is located at a predetermined distance of approximately 20mm, wherein an essentially point-type shadow on the scale (93) of thesighting device (66) is created when the spherical bead (92) isilluminated by the light source (24), the shadow being employed to readthe tilt angle of the eyeglasses, and wherein a horizontal line (95) ofthe scale (93), which line preferably matches the approximately 11° tiltangle of the eyeglasses (41) and is emphasized in thickness as thereference line, and wherein the additional horizontal scale lines (94,96, 97) above and below this reference line each represent a change inthe eyeglass tilt angle of approximately 5°.
 4. Device according to oneor more of claims 1 through 3, characterized in that a plurality ofpreferably approximately 10×10 to 20×20 pixels on the computer screen(34) are selected when determining the brightness center point of thecalibration points (62, 64) for the superposable frame (50) and/or ofthe reflection points (42, 44) of the light source (24) on the corneausing the square box, only those pixels of the square box being selectedto determine the brightness center point for which the brightness liesabove an externally selectable threshold, and the evaluation proceedingby way of weighted averaging in which the first sum is obtained from thebrightness of the selected pixels multiplied by the X-coordinate, asecond sum from the brightness of the selected pixels multiplied by theY-coordinate, and a third sum from the brightness of selected pixels,the X-coordinate of the brightness center point resulting from divisionof the first sum by the third sum, and the Y-coordinate of thebrightness center point resulting from division of the second sum by thethird sum.